Attachment for antennas to reduce operating frequencies



March 30, 1965 w. E. NETTLES 3,176,298

ATTACHMENT FOR ANTENNAS To REDUCE OPERATING FREQUENCIES Filed June l1, 1962 2 Sheets-Sheet 1 INVENTQR. M//urm E. /Vfrn 5 #Tram/EY March 30, 1965 W' E, NETTLES 3,176,298

ATTACHMENT FOR ANTENNAS TO REDUCE OPERATING FREQUENCIES INVENTOR, i| WALTER /Vfrnfs N N I n BY r WM( shi,

3,l76,298 ATTACHMENT FR ANTENNAS T REDUCE @PERA'iNG FREQUENCEES Walter E. Nettles, Denver, Solo. (S355 Tanque Verde Road, Rte. 2, Box 694m, yEricson, Ariz.) Filed .lune l1, 1962, Ser.. No. 261,346 l Claim. (Qi. 343-3722) This invention relates to an attachment for radio receiving and sending antennae for reducing the operating frequency of the antenna.

A conventional amateur radio station, usually referred to as ham stations, will usually employ a rotary directive, multi-band antenna designed to selectively operate on the ten meter, fifteen meter or twenty meter bands. During the eleven year sun spot cycle, there are intervals which after dark the ten, fifteen and twenty meter bands become inoperable except for ground wave and unusual skip operation. In such instances it is necessary to work at a lower frequency such as, for instance, in the forty, eighty, and one hundred and sixty meter bands prefen ably the `forty meter band. The cost and the space required for an additional directional antenna for the occasional longer wave operation is usually prohibitive for the average radio ham The principal object of the invention is to provide an attachment, two of which can be applied to a present multibrand antenna to enable the present antenna, to be operated on an additional lower frequency band without interfering with the antennas operation on the former bands and without change in or addition to the )resent single feed line.

Another object is to so construct the attachments that they can be quickly and easily applied to or removed from a present antenna without changing or disturbing the mechanical construction or normal electrical characteristics of the latter in any way.

Other objects and advantages reside in the detailed construction of the invention, which is designed for sim- These will become plicity, economy, and efficiency. more apparent from the following description.

In the following detailed description of the invention, reference is had to the accompanying drawing which forms a part hereof. Like numerals refer to like parts in all views of the drawing and throughout the description.

ln the drawing:

FlG. l is a plan view of a conventional, rotary directional 10, 15, meter antenna showing the attachments in place thereon to enable the antenna to operate on meters;

FIG. 2 is an enlarged side elevational view of one of the attachments, partially broken away to reduce the length of the view;

FIG. 3 is a still further enlarged longitudinal section through a wave trap as employed in the attachment; and

FIG. 4 is a similarly enlarged, longitudinal section through a loading coil as used on `the improved attachment.

In FIG. l, the elements of a typical multi-band rotary directional antenna are designated by numeral as follows: mast l0, boom l1, driven element l2, ten meter director 13, ten, fifteen and twenty meter director M, ten meter reector l5 and ten, fifteen and twenty meter reflector ld. The driven element 12, the director lll and the reflector 16 are provided with conventional ten meter traps i7 and with conventional fteen meter traps 1S. The energy is beamed in the direction of the arrow i9 in FIG. 1, for sending and will best receive beamed energy from the direction toward which the arrow points.

The extremities of the driven element l2 project op- United States Patent O positely outward from the traps 18 and it is to these outwardly projecting extremities that the attachments of the invention are attached.

For descriptive purposes, the attachments will be described for adapting the conventional ten, fifteen and twenty meter antenna to also operate on forty meters.

The attachments are similar and each, see FIGS. 2 and 3, is formed with a tubular connecting sleeve 20 adapted to slip over the extremity of the driven element l2. The sleeve 2i) is split, as indicated at 2l, so that it may be contracted and clamped on the extremity of the driven element by means of a clamp strap 22 and clamp screw 33. The outer extremity of the sleeve 20 is surrounded by a metallic bushing 24 over which a metallic capacitance tube 25 is tightly and rigidly fitted so as to project outwardly in axial alignment with the sleeve 2).

An insulating core 26 is tightly fitted Within the tube 25 and the core is axially drilled to receive the inner extremity of a first tubular antenna element 27. The tube 25 is preferably split so that they may be contracted about the core 26 by means of a second clamp strap 28 and clamp screw 2i?.

The first tubular antenna element 27, see FIG. 4, terminates in an insulating sleeve 3d from which a second tubular antenna element 3l axially projects. The sleeve 3@ is internally blocked, as indicated at 32, to prevent electrical contact between the elements 27 and 3l. A circular flange 33 of insulative material, as indicated, and which may be integral with the sleeve 3i) and blocking portion 32, surrounds the sleeve 3i). A third, tunable antenna element 34, see FIG. 2, is slidably mounted in the outer extremity of the second antenna element 3l and can be set at any desired projection therefrom by means of a suitable set screw 35. Y

lt will be noted that the metal tube 25 surrounding th inner extremity of the first antenna element 27 forms a capacitor as well as a support for the first antenna element. The capacitor is shunted by an open, coaxial, inductance coil 36 which is electrically connected at its inner extremity to the sleeve 20 by means of a connector 37 and at its outer extremity to the first antenna element 27 by means of a second connector 38.

For forty meter operation, the capacitance and the inductance are so designed as to provide a wave trap of low impedance to the forty meter frequency and infinite impedance to the twenty meter frequency of the driven element l2. At the twenty meter frequency, the trap will resonate and the first antenna element 27 will be divorced and insulated from the driven element l2 so that the latter will operate conventionally on the ten, fifteen and twenty meter bands as though the attachment were not present.

An open loading coil 39 surrounds the insulating sleeve 3) and is electrically connected at its inner extremity to the first antenna element 27 by means of a connector 4t) and at its outer extremity to the second antenna element 3l by means of a suitable connector 4l. The inductance coil 39 fits over and is physically supported by the circular flange 33 on the insulating sleeve 30. The loading coil is such as to provide the approximate inductance to cause the attachment to resonate in the forty meter band at any desired frequency between 7.000 kc. and 7.300 kc. The final tuning is accomplished by adjustment of the effective length of the third antenna element 34. All this has been accomplished by an extension of the driven element l2 of only a few feet, thus, keeping cost, weight and wind resistance to a minimum. The total added length is only approximately six feet.

Installation of the attachments is a relatively simple matter. It is only necessary to slip the sleeves 29 over the extremities of the driven element, director 1d and re- Y Y Y 3 l 'ecto'r 16, arid tighten them thereon by means of the clamp's'cre'v'vs 23. No'o'ther attachment is required.

The described antenna can then selectively operate on the ten, fifteen, twenty and forty'meter bands. On .the

forty meter band, the driven element operates independently without reflection ona ligure 8f pattern Ywhich is highly desirable in most instances on forty meters because of the so called round-table type of operation that is quite prevalent on forty metersas Wel-l as the other low frequency amateur bands of eighty and onehundred and sixty meters. Bychanging the loading coilinductance itis feasible tofconvert existingn tri-band,antennae, fed directly With'co-axialcableand not using any sort of a match such-as the so called gamma match, T match,v

etc., to operate as a shortened dipole and still maintain a reasonable standing waveratio, on conventional 52 ohm nominal impedance co-axial cable such as fRG-Sp/U, etc. The most practical application is for forty meters where the ,Q of the antenna, even though shortened, is such as to allow an impedance that permits almost unity coupling to the commonly used, Y commercially avail- Y I operation on its former bands, each of said attachments comprising: a connecting sleeve adapted to receive one of said extremities; an elongated metallic vcapacitance tube forming an axial extension of said sleeve; an antenna element positioned within and insulated from said tube and forming an axial extension from saidjtube, said element and said-tube forming a capacitance; an inductance coil surrounding said capacitance and shunting the latter be-y tween said sleeve andsaid antenna element, said inductance, coil having clamping terminals attached to the connecting sleeve and the antenna element, said capacitance and inductance providing high impedance to said former `bands and low impedance-to said addi-tional lowers vfrequency, each 'of' said attachments having a second antenna able RG-S/U feedlines as used by amateur radio s operators, s v Y v p Y As an example for forty meter operation, an inductance coil of 11 turns in parallel with the co-axial capacitor acts as a resonant circuitotfering infinite impedance at the frequency of the twenty meter, band. This inlnite impedancelis primarily resistive and therefore acts` as an insulator for the twenty 4meter frequencies of the con# f ventional antenna. A loading coil.39 of twenty-one turns offers additional reactance on forty meters requiring only relatively shortrst and second antenna elements- 27 andV 31 to resonate on forty meters. f

V he above invention converts existing. high frequencyV antenna systems for use `as-shortened dipoles ofVl/z-wave lengthen the lower frequency bands.

While a'speciciform of the. invention khas been described and illustrated herein,it is to be understood that.

the same may be varied within the scope Aof the appended'- claim, without departing from Vthe spirit of the invention. Having thus described the invention, what is claimed and desired to be secured 'by Letters Patent is: s s

Attachments for application Vto the two extremities of the driven element of a multi-band radio antenna to enable said an-tenna to be ,operated on an yadditional lower frequency .bandwithout interference with the antennas element in coaxial Valignment with the rst antenna element and insulated from the latter and a loading coil Y shunted between and surrounding the adjacent extremities of 'both antenna elements and providing anI inductance t'o cause said attachment toresonateat said additional lower frequency; and an insulating member in the form of a sleeve with a wall dividing the sleeve into two cylin- Y drical recesses, one antenna element:V being seated in one recess and the other antenna element being seated in the other recess, said loading coil surrounding the antenna element in spaced relation thereto and being connected at its ends respectively to said'antenna elements, said sleeve having a flange integral therewith and supporting an intermediate portion of-the loading coil.

Refeiences Cited bythe Examiner Y VOTHER REFERENCES The A.R.R.L. Antenna Book, pages 59 'and 60,copy

right 1960, by The American Radio RelayA League, I'nc., Lib. of Congress Catalog Card No. -8966rY HERMAN KARL sAALBAcmPr'imary Examinar. 

